Process for preparing lead alloys on which work is to be performed



I may be more easily, feasibly Patented dune 26,1928. UNHTED heiress rarsnr cranes.

REGINALD SCOTT DEAN AND'WILLIAMEWABT HUDSON, OF OAK PARK, ILLINOIS, JAS- SIGNORS 'lO WESTERN ELECTRIC COMPANY, INCORPORATED, 015 NEW YORK, N. "K,

A CORPORATION OF NEW YORK.

PROCESS FOR PREPARING LEAD ALLOYS ON WHICH WORK IS TO BE PERFORMED.

No Drawing. Application filed February This invention relates to a process for preparing lead alloys on which work is to be performed.

An object of this invention is to provide a process for preparing lead alloys on which work is to be performed whereby said work and efficaciously' accomplished.

Another object of this invention is to provide a process for working lead alloys more I quickly and with less incidental delay than quired for solidifying has heretofore been possible.

A further object of this invention is to provide a process for forming lead antimony articles of higher antimony content than has heretofore been possible with out the development of blisters, fractures, or other similar irregularities.

In describing the process which is the .basis of this invention reference will be made to the extrusion of cable sheath, but it is to be understood that the process of preparing the alloy can be efliciently employed wherever workof any type is employed to produce a lead alloy article.

Heretofore the process used for extruding lead alloys has been as follows: The required proportions of lead and alloying matter were melted in a kettle or melting pot. The molten lead alloy was then introduced into the cylinder of an extruding press, where it was allowed to solidify, the time rebeing in practice between six and ten minutes. As soon as the lead had solidified, it was extruded into the form desired. As an alternative the ingot was cast outside of the press and subsequently introduced into the press cold and extruded after it has been heated up in the press cylinder. For fast'extrusionit is necessary to work at as high a temperature-as possible. It is known that the plasticity of a metal'is 'approximately'doubled for a 10 G. rise in temperature. It follows that therate of exextrusion with a" given pressure and' orifice will be approximately doubled by a 10 C. rise of temperature. The advantage of axsin'g the highest'fpossib'le temperature is, t

lerefore, clear. In lead presses when the.

extrusion temperature was raised to permit more rapid extrusion, certain 'de fects such as blisters, cracks, splitsjand the like were encountered in the sheath formed. These defects are encountered more frequently when 5, 1924.. Serial in). m

the content of antimony or other alloying element is increased. I

It is known that when an alloy of lead and antimony is cast and rapidly cooled that the resulting alloy has areas of eutectic alloy and that as the antimony increases, these areas increase. It is reasonable to suppose that the defects referred to are caused at least inpart by the presence of these eutectic areas, since the eutectic becomes molten at a temperature below that of the remainder of the alloy.

Attempts have been made to increase the percentage of antimony in lead-antimony alloys. Such increase has had the effect of developing eutectic areas, which, it is supposed, cause the imperfections which appear on the extruded article. An attempt was madeto extrude at a lower temperature, but

difficulty was again experienced, due, it seems, to insufficient plasticity at temperatures below the eutectic melting temperature.

It was established in the investigation on which this invention is based that the solid solubility of antimony in lead at room temperature is approximately 1 per cent, and increases with the increases of temperature. At 240 (3., which is slightly below the eutectic fusing temperature, the solubility is about 2.5%. By heating ingots of lead-antimony alloys containing less than 3 per cent antimony for a sufficient length of time, it was found that a homogeneous solid solution f could be formed, the eutectic areas disappearing' For a more detailed description of a process for forming solid solutions of lead and antimony our co-pending application, Serial No. 690,716, filed February 5, 1924, may be referred to. i

Based on this discovery the process hereinafter described of extruding lead alloys has been developed. In carrying out this invention an ingot of lead-antimony alloy is cast, and then heated. or soaked for a period of time before extrusion. The ingot can then be placed in an extruding press and extruded at a-higher temperature, and vconsequently with greater celerity, without any apparent irregularities being developed. 'The time formerly required for themolten lead to solidify inthe press cylindeiflis also saved, the extrusion being almostycontinuous. In ad: dition this heating or soaking treatment will allow the use of an alloy having a greater antimony content, without the dificulties experienced in the use of that same alloy under the old method. A study of the article extruded from such a soaked or annealed ingot shows a disparity or total absence of eutectic areas.

Specifically a method employed in the extruslon of cable sheath is as follows: the ingot is cast outside of the extruding press and subsequently placed in an oven in which a temperature of 240 C. is maintained for 72 hours.

After this heating or soaking, the ingot is placed in an extruding press and immediate y extruded. Immediate extrusion is not necessary, however, since if the ingot is once heated for a sufficient length of time, it may be cooled and then by reheating for a comparatively short length of time, it may be used equally well. Good results may be obtained by varying the time and temperature of heating somewhat. The specific process above described has been adopted because universally good results seem to be obtained by it.

The explanation of the lack of eutectic areas in the cable sheath by means of this process and the coincident fact that such cable sheath shows none of the irregularities, such as blisters, cracks, or fractures, which appear in articles extruded under the old rocess, would seem to lie in the discovery that the solid solubility of the lead in antimony varies with the temperature of the alloy. It would seem that an annealing process gradually allows the proportion of antimony in solution in the lead to increase,

until the maximum amount at the given tem erature is reached.

1 is explanation is apparently borne out in the fact, since, as heretofore noted, eutectic areas are not noticed on the cable sheath extruded from the heated slug.

truded much more efiiciently by the use of this method.

Wherever alloying matter is used which forms a homogeneous solution, mixture, or compound with the lead rather slowly, and

.which forms such a solution, mixture or compound better at a higher temperature, this method has a beneficial use. This invention is present in any process where lead alloy is substantially all of the antimony present in the alloy.

3. A process for preparing lead-antimony alloys for extrusion, which consists in casting an ingot containing not more than 3% antimony, and heating said ingot at a temperature of 240 C. for about 72 hours.

A. A process for extruding lead-antimony alloys, which consists in initially casting an ingot, and heating said ingot at 240 C. for about 72 hours, placing said slug inan extruding press, and extruding.

5. A process for extruding lead-antimony alloys containing up to 3 per cent antimony, which consistsin casting an ingot of said alloy, heating said ingot until a substantially homogeneous solid solutionis formed, placing said ingot in an extruding press, and extruding.

6. A process for extruding lead alloys, which consists in casting an alloy ingot, forming said ingot into a solid solution by heating, and extruding.

7. A process for preparing lead alloys on which work is to be erformed, which consists in casting the alloys in the form of an ingot, and then heating said ingot at a temperature slightly below the fuslon temperature until a substantiall homogeneous solid solution is formed, .sai solid solution containing substantially allof the solute mater al present in the alloy.

8. A process for pre aring lead-antimony alloys for extrusion, w ich consists in cast ing an ingot of the alloy, and heating said ingot at a temperature slightly below the fusion temperature until a substantially homogeneous solid soltion is formed, said solid solution containing substantially all of the antimony present in the alloy.

9. A process for preparing lead-antimony allo s for extrusion, which consists in casting an ingot of an alloy containing about 2.5% antimony, and heating said ingot at a tem perature slightly below the fusion temperature for about 72 hours.

In witness whereof, .wr hereunto subscribe our names this 22ndday of J anuar REGINALD SCOTT DEAN. WILLIAM EWART HUDSON. 

